High speed boat hull

ABSTRACT

A high-speed boat hull for preferred use with a hydrojet engine having a plurality of substantially parallel strakes on the surface of the hull commencing from aft of the bow and all but the two center-most strakes running to the stern, the cross section of the strakes presenting a series of inwardly sloping steps to raise the hull in the water, direct the water flow inward toward the center of the hull, and assist in turning the hull when operating at high speeds.

United States Patent Weeks [451 Dec.4, 1973 [22] Filed: June 9, 1972[21] Appl. No.: 261,300

[52] US. Cl. 114/56, 1l4/66.5 P, 9/6, 9/6.5, 115/11 [51] Int. Cl. B63b l/34 [58] Field of Search 114/56, 66.5 R, 66.5 P,

[56] References Cited UNITED STATES PATENTS 293,714 2/ 1 884 Bymes 9/62,965,061 12/1960 Bank et al.... 3,137,261 6/1964 Noe 3,288,100 11/1966Cox et a1. D214,767 7/1969 Granholm D71/1 HIGH SPEED BOAT HULL Inventor:Smith Weeks, Fresno, Calif.

Assignee: Belmont Boats, Inc., Fresno, Calif.

FOREIGN PATENTS OR APPLICATIONS 11/1964 France 9/6 OTHER PUBLICATIONSLevi, Renato, Speed and High Deadrise, Yachts and Yachting, pp.1421-1424, June 20, 1969 (Great Britain).

Primary Examiner-Duane A. Reger Assistant Examiner-D. C. ButlerAttorney-Karl A. Limbach et al.

[57] ABSTRACT A high speed boat hull for preferred use with a hydrojetengine having a plurality of substantially parallel 8 Claims, 6 DrawingFigures FAH'NIEDUEC 419-75 I 3,776,168 I sum 1 a; 2

- i sum as? 2 HIGH SPEED BOAT HULL BACKGROUND OF THE INVENTION originsof any of the useful arts. With each introduction of a new power sourcefrom paddle, to sail, to propeller the configuration of the hull hasbeen continually redesigned to take full advantage of the particularpower source employed. As power sources for smaller craft improved tothe powerful high-speed engines of modern craft, the refinements havebecome more sophisticated.

The introduction of the hydrojet engine which operates by pumping a highvolume, high velocity stream of water from the stern of a hull, hascreated particular problems not presented by the more common propellerengines. Principally, a hull driven by a hydrojet engine does not havethe advantage of a rudder projecting into the water which provides acontrol surface for highspeed turns and a limitation to side slip.

Irregular hull surfaces and projecting vor step-like strakes have beenused on prior art hulls for controlling maneuverability. However, noneof the prior art designs have been found to be as suitable forhigh-speed maneuverability using a hydrojet power source as the hulldesign of the present invention. Generally, strakes are extended too farforward and interfere with controlled turns, or are of insufficientwidth to provide any significant lift to the hull.

SUMMARY OF THE INVENTION The high-speed hull of my invention employs aplurality of strategically located, step-like strakes to control thewater flow under the hull. The step-like strakes are formed integralwith the hull and are parallel to one hull of the invention is describedin greater detail in the following specification and in the attacheddrawings.

BRIEF DESCRIPTIONOF THE DRAWINGS FIG. 1 is a side elevational view ofthe hi gh-speed hull and hydrojet nozzle.

FIG. 2 is a plan view of the hull of FIG. 1.

FIG. 3 is an enlarged sectional view taken on the lines 33 in FIG. 2.

FIG. 4 is an enlarged sectional view taken on the lines 4-4 in FIG. 2.

FIG. 5 is an enlarged perspective view of the hull of FIG. 1.

FIG. 6 is a schematic view of the hull of FIG. I in a high-speed turn.

shown for a hydrojet craft capable of speeds of 60 another running fromsubstantially aft of the bow and,

all but the two centermost strakes, running to the stem.

The two centermost strakes end forward of the sternto allow center linemounting of a water intake for a hydrojet propulsion system.

From a cross section perspective the strakes are steplike in form, andare sloped slightly inward'from the horizontal whereby correspondingstrakes on opposite sides of the keel present a composite concavesurface as opposed to the generally convex surface of the curved hull.This concave surface directs 'the flow of water under the hullcenterward, which both increases lift and enhances the water flow andsupply atthe hydrojet intake.

In addition to these characteristics, the strakes greatly enhance thehigh-speed maneuverability of the hull. The vertical faces of thestep-like strakes form a plurality of low profile, longitudinalrudders'and' pre-' vent excessive sideslip on high speed turns. It hasbeen discovered, however, that the strakes must-commence substantiallyaft of the bow. The location of the forward knots. The preferredembodiment illustrated has a length of 18 feet, 1 inch. The particulardimensions detailed in this description are not critical, butratherprovide a basis for determining the relative configuration of the hull.If the length of the hull is altered the other primary dimensions shouldbe altered in general proportion to the length. The craft shown ispowered by a high-power inboard engine 12 which drives a pump (notshown) in a hydrojet propulsion unit 14. Water ejected at a nozzle 16 atvolume and high velocity generates a Newtonian reaction on the hull l0propelling the hull through the water. To turn the craft, the directionof the nozzle 16 is altered, shifting the direction of reaction forceson the hull and causing the craft to turn by action of the transverseforces at the stern. Since turning is accomplished wholly by reactionforces on the hull, and not by direct forces from water flow on'arudder, it is necessary that the hull incorporate means to inhibitsideslip caused by the straight line momentum'of the craft prior toinitiating a turn.

The means employed to inhibit sideslip comprise a series ofsubstantially parallel strakes. Referring to FIG.

2, .corresponding'strakes on each side of the centerline of the hull arefor convenience identified as chine strakes 18,.outer strakes 20, innerstrakes 22 and center strakes 24. The strakes are uniformly spacedapproximately 9 inches from one another, on a hull having a beam ofinches at the transom 26, the configuration of which is shown in FIG. 3.The center strakes are spaced 16 inches apart and as shown in FIG. 2 endadistance measuring 50 inches from the transom 26.

Referring to the sectional view of FIGS and the sectional view of FIG.4, the strakes are step-like in form having an outward vertical face 28and an incline face 30 as shown in the exemplars. The outward verticalfaces 28-of the chine strakes 18 are composite with the sides 32 of thehull.

The incline faces 30 of the chine strakes have an inwardly sloping angleof approximately 21 from the horizontal. Similarly, the incline faces 28of the outer strakes 20, inner strakes 22, and center strakes 24 areinwardly sloping, but with a lesser angle from the horizontal of onlyapproximately 8. The angle of slope of the incline faces 30' increasesthe height of the vertical faces 28 and provides a larger bite to thestrakes than merely horizontal faces.

The greater angle of the chine strakes l8 permits a bite to be taken bythe incline face 30a of the inside chine strake 18a on a banking turn asshown in FIG. 6. Because of the overall V-shaped contour of the hull,the craft banks on a turn, as shown in FIG. 6, raising the outside chinestrake 18b partially out of the water and cutting the inside chinestrake 18a deep into the water. The drag on the incline face 30a of thechine strake 18a, from a perspective of induced transverse moments onthe hull, partially compensates for the drag on the vertical faces 28bof the three outer strakes remaining in the water, and thereby aids instabilizing the hull from overturning. The transverse drag on the hullin a sharp turn caused by the vertical faces 28b on the outside strakesand to a lesser extent the incline faces 30a on the inside strakes,particularly the chine strake 18a, inhibits sideslip, the direction ofwhich is indicated by the arrow in FIG. 6.

importantly, the strakes as shown in FIGS. 1 and 2, commencesubstantially aft of the bow 34, running only 10 feet 4 inches of thetotal 18 feet 1 inch length of the hull. The forward third of the hullis a smooth gradually sloping surface designed to allow waves from anydirection to slide under the hull. The absence of strakes in the forwardthird of the hull enhances maneuverability by eliminating irregularitieswhich can catch on a wave or wake and flip the craft in a high-speedturn. The lead end of the strakes are tapered into the smooth surface ofthe forward portion of the hull to provide a gradual transition from thestraked portion to the smooth portion. At the transom the strakes arerounded.

In addition to inhibiting sideslip in high-speed turns, the strakescontrol the water flow under the hull by channeling the flow parallelwith the keel or center line of the hull. Customarily; a V-shape in ahull permits a greater turning ability, but because it divides the waterflow, it causes the hull to ride deeper in the water than a flat bottomhull. The strakes with their wide incline plified in FIG. 5. At highspeeds, the channels and vertical faces of the strakes inhibit flowdivision by the hull and cause the relative flow to be substantiallyparallel with the center line of the hull. The incline faces of thestrakes compensate in part for the sloping hull by directing water flowinward toward the center of the hull. This is a particularly importantfeature for the hydrojet propulsion unit 14 which requires a largesupply of water at its intake 42 shown in FIGS. 1, 2 and 5.

The intake 42 is located aft of the ends 44 of the center strakes 24.Water, directed in the path of the intake 42, guided by aid of theincline faces 30 on the center strakes 24, is sucked by a pump (notshown) in the hydrojet propulsion unit 14, and ejected at high velocityatythe nozzle 18 thereby propelling the craft at high speed.

While the invented hull is designed primarily for compatability with ahydrojet engine, it is not intended to so limit theinvention to thismeans of propulsion.

What is claimed is: i i

l. A high-speed boat hull with a bow and a transom and with a centerlinerunning from the bow to the middle of the transom, said hull comprising:

a forward portion with a smooth surface approximately one third thelength of the hull and an aft portion having a plurality ofsubstantially parallel strakes said strakes having a first vertical faceand a second inwardly incline face to raise the hull in the water toassist in turning the hull when operating at high speeds and to directportions of the relative flow of water inward toward the center of thehull; said hull including a hydrojet intake located in the aft portionof the hull, forward of said transom on the centerline of said hull.

2. The hull of claim 1 wherein said smooth surface is greater than onequarter but less than one half the length of the hull.

3. The hull of claim 1 wherein said strakes include two center strakesarranged on said aft portion of the hull on each side of the centerlineand terminating forward of said hydrojet intake.

4. The hull of claim 3 wherein the strakes other than the two centerstrakes run the length of the aft portion of the hull and terminate atthe transom.

5. The boat hull of claim 4 wherein said incline face has an angle fromthe horizontal exceeding 5.

6. The boat hull of claim 4 wherein said incline face has a widthexceeding 3 inches.

7. The boat hull of claim 4 wherein said strakes have a tapered lead endand a rounded trailing end.

8. The boat hull of claim 4 in combination with a hydrojet power unitfor propelling said hull at high speeds.

k I. ll III

1. A high-speed boat hull with a bow and a transom and with a centerlinerunning from the bow to the middle of the transom, said hull comprising:a forward portion with a smooth surface approximately one third thelength of the hull and an aft portion having a plurality ofsubstantially parallel strakes said strakes having a first vertical faceand a second inwardly incline face to raise the hull in the water toassist in turning the hull when operating at high speeds and to directportions of the relative flow of water inward toward the center of thehull; said hull including a hydrojet intake located in the aft portionof the hull, forward of said transom on the centerline of said hull. 2.The hull of claim 1 Wherein said smooth surface is greater than onequarter but less than one half the length of the hull.
 3. The hull ofclaim 1 wherein said strakes include two center strakes arranged on saidaft portion of the hull on each side of the centerline and terminatingforward of said hydrojet intake.
 4. The hull of claim 3 wherein thestrakes other than the two center strakes run the length of the aftportion of the hull and terminate at the transom.
 5. The boat hull ofclaim 4 wherein said incline face has an angle from the horizontalexceeding 5*.
 6. The boat hull of claim 4 wherein said incline face hasa width exceeding 3 inches.
 7. The boat hull of claim 4 wherein saidstrakes have a tapered lead end and a rounded trailing end.
 8. The boathull of claim 4 in combination with a hydrojet power unit for propellingsaid hull at high speeds.